Tendinopathy

Definition & Terminology

• Tendinitis — historically implied acute inflammation
• Tendinosis — now preferred; reflects the true pathology: a degenerative process with few or no inflammatory cells on histopathology

Epidemiology

• ~30% of all musculoskeletal evaluations in emergency or urgent care settings involve tendinopathy
• The incidence is rising, paralleling a 3.6% increase in athletic/fitness participation over a 12-year period
• Accounts for the 5th most days away from work among non-fatal injuries in the U.S. (~14 days average)
• Economic impact: estimated ~$800 billion in healthcare costs over 3 years
• Workers with 25–35 years of service are 7.1× more likely to develop tendinopathy

Pathophysiology

Acute Tendon Healing Stages

1. Hemorrhagic phase — blood accumulates and clots
2. Inflammatory phase — neutrophils and macrophages perform phagocytosis of necrotic material
3. Proliferative phase — extrinsic and intrinsic cells migrate; type III collagen synthesized (thinner, less tensile strength than type I)
4. Formative phase (up to 2 months) — collagen fibers mature and orient to handle tensile forces
5. Remodeling phase — normalization of type I:III collagen ratio; physiologic load reintroduced

Key Concept — Optimal Loading

• Complete immobilization is relatively contraindicated — atrophy worsens outcomes
• Optimal loading (graduated, incremental rehabilitation with eccentric training) is now the preferred approach

Etiology & Risk Factors

Intrinsic Factors

• Age, female sex, blood type O
• Adiposity, tobacco use
• Malalignment, joint laxity, muscle weakness/imbalance

Extrinsic Factors

• Ergonomics, abnormal movement patterns
• Excessive activity duration, frequency, or intensity
• Equipment changes, environmental conditions

Drug-Related Causes

Systemic Causes

• Diabetes mellitus, gout, coronary artery disease
• Rheumatologic disorders
• Infectious (e.g., Mycobacterium)

Common Sites

Common sites of tendinopathy and bursitis — Rosen's Emergency Medicine

Clinical Features

• Non-radiating, localized pain at the tendon site — most common symptom
• Pain worse after rest (morning stiffness) or with loading
• History of repetitive stress (occupational or sports-related, often weeks to months prior)
• Ask about fluoroquinolone/statin use, systemic illness, recent ergonomic changes

Differential Diagnosis

• Tendon rupture
• Ligamentous injury
• Inflammatory arthritis (e.g., rheumatoid)
• Stress or avulsion fracture
• Bursitis, septic arthritis
• Tenosynovitis
• Osteochondrosis (e.g., Osgood-Schlatter)
• Tumors

Diagnosis

• Clinical in most cases
• Plain radiographs: useful to identify calcific tendinopathy or exclude bony pathology (~20% show calcification in lateral epicondylitis)
• Ultrasound: recommended first-line imaging; identifies tendon disruption/rupture, useful for guided procedures (e.g., calcific tendinopathy lavage)
• MRI: gold standard for detailed soft tissue evaluation

Management

Box: Components of Tendinopathy Management

1. Identify and eliminate the cause
2. Analgesics — short-term NSAIDs
3. Protection + relative rest (avoid complete immobilization)
4. Optimal loading — ergonomic alteration, graduated eccentric exercises
5. Ice, compression, elevation
6. Patient education and behavior modification
7. Vitamin D supplementation
8. Referral for rehabilitation (PT, sports medicine, orthopaedics)

Pharmacological Adjuncts

Surgical

• Indicated for tendon rupture (primary repair) or refractory cases that have failed conservative treatment
• Débridement for recalcitrant cases (e.g., patellar tendinopathy)

Prognosis

• Overuse tendinopathies: full recovery typically within 3–6 months
• Recurrence common — 49% of athletes with patellar tendinopathy; 40–50% of rotator cuff tendinopathy patients symptomatic at 6–12 months